Stabilized epinephrine-type compound, and process of stabilizing it



Patented July 7, 1936 UNITED STATES PATENT OFFICE STABILIZED EPINEPHRINE-TYPE COM- POUND, AND PROCESS OF STABILIZ- ING IT poration of Indiana No Drawing. Application March 26, 1934, Serial No. 717,428

14 Claims.

It is the object of my invention to obtain a more effective stabilization than has heretofore been obtained of epinephrine (adrenalin), and of other epinephrine-type compounds which like epinephrine have a substituted-amino group, or an amino group (NHz), connected to a monoor poly-hydroxy phenolic group through an intervening two-carbon chain having a hydroxy group on the carbon atom adjacent to the phenolic group, including compounds structurally and/or optically isomeric with epinephrine; and particularly to protect the substance against the effects of oxygen and heat.

It is well recognized that when solutions of the now-known epinephrine salts, such as the hydrochloride, are kept in air, they slowly acquire a gradually deepening pink color, and that later a black solid separates; especially under the action of heat. This reaction, which is one of oxidation by oxygen, is usually markedly accelerated by heating the epinephrine hydrochloride solution to 100 C., whereupon within 15 to 30 minutes a heavy black precipitate usually forms.

This tremendous instability of epinephrine has forced manufacturers of epinephrine preparations to resort to the following expedients to prevent deterioration a. The hydrogen ion concentration of the solution is maintained at pH2 to pH3.

b. The material is kept in dark bottles.

0. The solutions are ordinarily saturated with carbon-dioxide gas, to decrease the amount of oxygen contained in the solution and thereby to decrease the oxidation of the epinephrine.

Other reagents are also added, by Various manufacturers, in an attempt to promote stability.

A somewhat similar situation exists with respect to the stability of 3,4-dihydroxy-nor-ephedrine, which is also often called 3,4-dioxy-norephedrine; which is isomeric with epinephrine, as the following structural formulas show:

Epinephrine:

l l gerv OH H CH3 HO 3,4-dihydroxy-nor-ephedrine:

But none of these expedients, nor all of them together, are very efiective; as is indicated by the fact that manufacturers of epinephrine preparations ordinarily suggest that solutions of those preparations be rejected it they develop a pink color; and by the fact that to sterilize such preparations they are ordinarily heated for only a 5 few brief moments, instead of for the much longer time which is commonly deemed necessary for efiective sterilization of pharmaceutical products.

I have now found that epinephrine and its compounds, and similar types of isomeric and 10 epinephrine-like substances containing the hydroxyl groups on the benzene ring in different positions or including only one hydroxyl group on the benzene ring-all of which may be included in the term epinephrine-type substances- 15 can be efiectively protected against atmospheric oxygen and heat by the use of sulfhydryl derivatives or tautomeric substances which in one tautomeric form are sulfhydryl compounds.

There are three distinct classes of these stabiliz- 0 ing substances that tend to stabilize epinephrine and epinephrine-like substances. These are:

1. Organic thiol acids.

2. Substances of the mercaptan type.

3. 'I'automeric substances which in one tautomeric form are compounds containing thiol (sulfhydryl) groupings. Of these tautomeric substances, the thioureas, including thiourea itself and its nitrogen-substituted derivatives, are the most desirable.

By either oi the terms a compound containing a sulfhydryl group and a thiol compound I mean to include all three of these classes.

While the effects of any of these reagents are essentially the same-the inactivation of the oxygen of air through the efiect o! the thiol groupthe procedure of preparing active and stable epinephrine and epinephrine-like preparations varies according to the type of stabilizing reagent employed. This will become clear in the discussion of the examples given hereinafter. It is sufficient here to say that in using the first class of substances a water solution or suspen-' sion of epinephrine, or epinephrine-like base is treated with an organic thiol acid, which combines with such base to form a corresponding salt, a new type of compound; and that in using the second and third class of substances, 9. watersoluble salt oi epinephrine or of the epinephrinelike base is used, and the stabilizing substance is added to a solution of that salt. That is, the stabilizing substance may or may not be part of the molecular structure of the epinephrine or epinephrine-like preparation. In other words, '55

aomyamgmitne a I 'siflp yd iv i ny ae tic; on

and epinephrine-dike bases is pH 3. It is possible to obtain this optimum hydrogen ion. concentration by controlling the quantity of organic thiol acid used-usually by Mer cantem -n of water, and the salt formed either by adding hydrochloric acid if the hydrochloride salt is desired or by adding the desired organic thiol adding to one mole of the epinephrine base about acid if a thiol-acid salt is desired. In both inthree moles of the thiol acid. stances the hydrogen ion concentration is ad- In the second and third classes of stabilizajusted. to the value indicated by varying the tion compounds, the stabilization may be of an amount of acid added; and in the case of stabiinorganic-acid salt of epinephrine or an epinephlizers in classes 2 and 3, the amount of stabirine-like base, such as nor-epinephrine or 3,4- lizer added is indicated. In each case the dihydroxy-nor-ephedrine, with no direct entrance epinephrine or epinephrine-like compound, with of the sulfhydryl group into the molecule with whatever reagent is added, is heated atatemperathebase save that which may occur incidentalture of 100 C. in a sealed tube containing some ly in connection with ionization of these moleair, and the tube is examined at various time cules. These second and third classes of thiol intervals.

Table of comparative stabilit'ies Epinephrine compound Stabilizing reagent added pH 3 332 Result 1. Epinephrine hydro- None. Control. 3.0 lhonr. Dark colored solution.

chloride.

6.0 ihonr. Darkeoloredsolution. 7.0 lhonr. Solution turned pink while BE was adjusted-i hr.

lack ppt.

'zEpinephrlne p-Suihydryi phenylsultonio 3.0 13 hours. Colorless solution.

sci

5.2 lhour. Faint yellow color.

- 6.0 lhour. Faint yellow color. 3. Epinephrine. Thioglyoollic acid. 3.0 15 hours. Colorless solution. I 5.0 10% hours. Faint yellow color.

6.2 iho'or. Light yellow color.

Iii

Table of comparative abilities-continued Epinephrine compound Stabilizing reagent added pH {5:22 Result 4. Epinephrine. B-sulihydryl propionic acid. 3. 0 10 hours. Colorless solution.

5. Epinephrine. Thiosalicylic acid. 3.0 2 hours. Colorless solution.

6. Epinephrine. Thiolectic acid. 3.0 10 hours. Colorless solution.

7. Epinephrine. Various isomeric sulihydryl 3. 0 2-10 hours. olorless solutions.

naphthalene sulionic acids. 8. Epinephrine hydro- Ethyl mercaptan. 3. 0 4 hours. Slightly 1 M Solution.

chloride. (0.1 g.)

8. 0 1 hour. Pink colored solution.

' 7. 0 3 hours. Dark colored solution. 0. Epinephrine hydro Benzyi merceptan (0.1 g.). 3.0 7houra. Solution colorless, but slightchloride. ly turbid due to insolubility oi benzyl-mercaptan.

6. 0 7 hour Colorless solution. slightly opalescent.

7. 0 7 hours. Practically colorless solution. with only slight turbidity, due to insolubility oi mercapten in water.

10. Epinephrine hydro- Thiophenol (0.1 g.). 3.0 711mm, Solution colorless, but slightchioride. 1y turbid due to insolubility oi thiophenol.

6. 0 7 hours. Colorless solution, slightly opelescent.

7. 0 7 hours. Pink colored solution slightly turbid.

11. Epinephrine hydro- Thiosinamine (eilyl thiourea) 3.0 8 hours. Colorless solution.

chloride. (0.2 g).

3.0 11 hours. Colorless solution with faint turbidity.

4. 0 14 hour. Pink colored solution.

12. Epinephrine hydro- Thiourea (0.1 g.). a. o 1 hour. F nt yellow colored Soluchloride. tion.

3.0 4 hours. Definite yellow colored solution.

13. Epinephrine hydro- Thiocresol (0.1 g.) 3.0 8 hours. Colorless solution with slight chloride. turbidity.

14. Epinephrine hydro- Thiosemicarbazide hydrochlo- 3.0 8 hours. Colorless solution.

chlori e. ride (0.1 g.)

15. 3,4-Dihydroxy-nor- None. Control. 3.0 4hours. Black precipitate formed at egirednne hydrothe end oi the first hour. 0 oride. Compound completely decomposed at the end oi iour hours.

16. 3,4-Dihydroxy-norp-Sulihydryl-sulionic acid. 3.0 14 hours. Colorless solution.

ephedrine.

17. 3,4-Dihydroxy-nor- Thiourea (0.1 g.). 3. 0 14 hours. Colorless solution.

ephedrine hydrochloride.

18. 3.4-Dihydroxy-nor- Thiosinamine allyl thiourea) 3.0 14 hours. Colorless solution.

eglhedine hydro- (0.2 g). c Oll e.

darkening, or any formation of a black precipitate. With the stabilizing reagents which contained thiol groups or which tautomerize to compounds having thiol groups, whether or not the thiol compound entered directly into chemical combination with the epinephrine or with the 3,4-dihydroxy-nor-ephcdrine, there is at most only a relatively slight deterioration, even at the higher pH values although even with these stabilizing reagents the best effects are obtained if the hydrogen ion concentration is maintained in the neighborhood of pH3.

While I am not certain what the precise nature is of the protective action due to the presence of suifhydryl groups, my theory of such action is I that because the sulfhydryl groups are easily oxidized (by the oxygen of the air) to disuifide compounds, they tend to react with any oxygen which may be present; and thus prevent the oxyson from acting upon the epinephrine or epinephrine-like substance. Whether or not this is the correct theory of the action, I have found as a fact that the presence of compounds containing the sulfhydryl group do serve very efiec-= tively to stabilize epinephrine and epinephrine- Bil 3. The process of producing a stable water solution of a salt of an epinephrine-type compound; which consists in producing a reaction or the epinephrine-type base with a thiol acid to produce a stable water-soluble salt.

4. A new composition of matter, consisting of a salt formed by the reaction of an epinephrinetype compound with an organic thiol acid.

5. The process of stabilizing a solution containing a salt of epinephrine; which consists in having present in such solution a compound containing a sulfhydryl group.

6. The proces of stabilizing a water solution of a salt of epinephrine; which consists in adding a thiol compound to such solution.

7. The process of producing a stable water solution of a salt of epinephrine; which consists in producing a reaction of the epinephrine base with a thiol acid to produce a stable water-soluble salt.

8. A new composition of matter, consisting of a salt formed by the reaction of epinephrine with an organic thiol acid.

9. The process of stabilzing a solution containing a salt 01! 3,4-dihydroxy-nor-ephedrine; which consists in having present in such solution a compound containing a sulihydryl group.

10. The process of stabilizing a water solution of a salt of 3,4-dihydr0xy-nor-ephedrine; which consists in adding a thiol compound to such solution.

11. The process of producing a stable water solution of a salt of 3,4-dihydroxy-nor-ephedrine; which consists in producing a reaction of the 3-4- dihydroxy-nor-ephedrine base with a thiol acid to produce a stable water-soluble salt.

. 12. A new composition oi. matter, consisting of a salt formed by the reaction of 3,4-dihydroxynor-ephedrine with an organic thiol acid.

13. The process of stabilizing a solution containing a salt of an epinephrine-type compound; which consists in' having a thiourea present in such solution.

' 14. The process of stabilizing a solution containing a salt of an epinephrine-type compound; which consists in having thiourea present in such solution.

MORRIS S. KHARASCH. 

